Development of a wideband waveguide diplexer for simultaneous observation at 210-375 GHz

Sho Masui; Taisei Minami; Masanari Okawa; Yasumasa Yamasaki; Koki Yokoyama; Shota Ueda; Yutaka Hasegawa; Atsushi Nishimura; Toshikazu Onishi; Hideo Ogawa; Takafumi Kojima; Alvaro Gonzalez

doi:10.1117/12.2561355

13 December 2020 Development of a wideband waveguide diplexer for simultaneous observation at 210-375 GHz

Sho Masui, Taisei Minami, Masanari Okawa, Yasumasa Yamasaki, Koki Yokoyama, Shota Ueda, Yutaka Hasegawa, Atsushi Nishimura, Toshikazu Onishi, Hideo Ogawa, Takafumi Kojima, Alvaro Gonzalez

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Proceedings Volume 11453, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X; 114534F (2020) https://doi.org/10.1117/12.2561355
Event: SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only

Conference Poster

Abstract

The 1.85-m mm-submm telescope has been operated at Nobeyama Radio Observatory to observe molecular clouds in the nearby Galactic Plane based on the molecular lines of ¹²CO, ¹³CO, C¹⁸O(J = 2–1). We are planning to relocate the telescope to a site (∼2,500 m) at the Atacama Desert in Chile and to newly install a dual-band receiver for simultaneous observations of lines of CO isotopes with the transitions of J = 2–1 and J = 3–2. In order to achieve this goal, we have developed a wideband diplexer to separate radio frequency (RF) 211–275 GHz (ALMA Band 6) and 275–373 GHz (ALMA Band 7). We adopted a waveguide type FrequencySeparation Filters (FSF) as the basic concept of the wideband diplexer in 210–375 GHz. The wideband diplexer (α) has already been fabricated and measured as the prototype, and we thus obtained reasonable performance in the CO lines band. On the other hand, the measurement result indicates the return loss is relatively worse in 280–300 GHz, although it doesn’t affect the simultaneous observations of 230 GHz and 345 GHz band. We carried out 3D shape measurement with an optical microscope, and then, found that there are machining errors in the parts of the resonator in High Pass Filter. The analysis based on electromagnetic simulation reveals that the errors significantly affect return loss around cut-off frequency. In this paper, we describes the design of the waveguide diplexer, S-parameter measurement, and detailed analysis to verify the discrepancy between simulation and measurement.

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Sho Masui, Taisei Minami, Masanari Okawa, Yasumasa Yamasaki, Koki Yokoyama, Shota Ueda, Yutaka Hasegawa, Atsushi Nishimura, Toshikazu Onishi, Hideo Ogawa, Takafumi Kojima, and Alvaro Gonzalez "Development of a wideband waveguide diplexer for simultaneous observation at 210-375 GHz", Proc. SPIE 11453, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy X, 114534F (13 December 2020); https://doi.org/10.1117/12.2561355

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